1. Field of the Invention
The present invention relates to a honeycomb structure body having a plurality of hexagonal cells arranged in a lattice shape and a manufacturing method thereof, and in particular, relates to a honeycomb structure body having a plurality of hexagonal cells in which each hexagonal cell is surrounded by a hexagonal cross-sectional cell wall composed of six sides.
2. Description of the Related Art
A conventional honeycomb structure body (as a monolithic support) has a plurality of square-shaped cells placed in a lattice arrangement and is used as a catalyst support and the like in an exhaust gas purifying filter for purifying particulate matters (PM) involved in exhaust gas emitted from an internal combustion engine such as a diesel engine and a gasoline engine mounted on a vehicle. Each cell in such a conventional honeycomb structure body has a square cross-sectional shape. For example, Japanese patent laid open publications JP H7-39761, JP 2000-237602, and JP 2002-321210 have disclosed such a conventional honeycomb structure body.
It has been typical to employ square shaped cells (or square cells) in a honeycomb structure body because of easy making its die for use in an extrusion molding and of manufacturing efficiency. However, such square cells forming the conventional honeycomb structure body involves a drawback to support excess amount of catalyst at four corners of each square cell wall (or each square partition wall) when the catalyst is supported on the square cell walls of each square cell. This excess amount of catalyst at four corners in each square cell further prevents the smoothing flow of exhaust gas.
Recently, a ceramic honeycomb structure body having hexagonal cross-sectional cells has been proposed in order to increase the purifying ability to purify the exhaust gas emitted from an internal combustion engine mounted on a vehicle. Such a ceramic honeycomb structure body has a plurality of hexagonal cross-sectional cells (hereinafter, referred also to as “a hexagonal honeycomb structure body”) and each hexagonal cell is capable of supporting a uniform amount of catalyst on its cell wall and of flowing the exhaust gas therethrough smoothly. Such a hexagonal cell can increase the purifying capability in the amount of catalyst, a pressure loss, the amount of exhaust gas of hydrocarbons and the like.
However, such a ceramic honeycomb structure body having a plurality of hexagonal cross-sectional cells has not flexibility to escape or distribute a stress applied from the inside and outside of the ceramic honeycomb structure body because each side of the hexagonal cross-sectional cell wall is formed in a straight line shape. Thereby, damage and cracking occur by the stress applied from the inside or the inside of the ceramic honeycomb structure body when such a hexagonal ceramic honeycomb structure body is mounted on a vehicle, or occur by vibration and thermal impact while mounting on a vehicle. In other wards, such a conventional hexagonal ceramic honeycomb structure body does not have a high flexibility to applied stress, does not have a high durability and a thermal shock resistance during the use.